More On Climate Change

In Rudy Baum’s editorial “Climate Schizophrenia,” he concludes: “What amazes me about climate-change skeptics and deniers is their rejection of the principle of Occam’s razor. CO2 is a greenhouse gas, its atmospheric concentration has been rising for 150 years, Earth’s temperature is rising—these are empirical facts. Why do some individuals go to such lengths to deny their connection?” (C&EN, Sept. 5, page 5).

There are two main reasons to investigate the connection: first, correlation is not causation (a point that many seem to miss these days), and though Occam’s razor may be a nice tool for formulating hypotheses, it is not a means of testing them, and second, the connection is hugely important on many different scales. One thing that is relatively well agreed upon in the contentious debates is that reducing CO2 severely below 1990 levels is likely to be very expensive. (Many would argue, however, that the expense is less than the cost of doing nothing if greenhouse gases really are the key reason for unchecked warming, accelerated snowpack and glacier melt, increased catastrophic storms, etc.).

The Intergovernmental Panel on Climate Change’s (IPCC) “Climate Change 2007: The Physical Science Basis” (www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf) conveys the complexity of the science, provides extensive scientific information, and does not invoke Occam’s razor in making its “Summary for Policymakers” conclusion that “most of the observed increase in global average temperatures since the mid-20th century is very likely [>90%] due to the observed increase in anthropogenic greenhouse gas concentrations.” That being said, they chose “very likely” rather than stronger expressions of accuracy they use elsewhere: that is, “extremely likely” (>95%) and “virtually certain” (>99%).

For many, very likely is not good enough when you are talking about spending trillions of dollars (especially in the current economy), and unlike what Baum’s editorial infers, it’s not just nonscientists who believe that the “very likely” conclusion still merits further study. As Stephen Ritter reported in the article “Global Warming and Climate Change,” key skeptics are not debunking global-warming theory or CO2’s role as a greenhouse gas but are instead questioning the extent to which greenhouse gases are resulting in the observed global-warming trends and climate changes (C&EN, Dec. 21, 2009, page 11).

Since publication of the 2007 IPCC report, studies have been published by scientists in peer-reviewed journals (and referenced by Science) that identify black carbon as being responsible for much more of the warming than previously thought; conclude that random wind-induced circulation changes in the oceans (rather than global warming) were the dominant cause of recent ice losses in glaciers; indicate that greenhouse gases are not the cause of unusual hurricane/tropical cyclone activity; and so on. There are those who disagree with these studies as well. It isn’t fair to say these are the final decisions on these matters, nor do they debunk IPCC. Skeptical scientists, however, are right to question, and despite what Baum saw at the conference he attended, they are not all unqualified nonscientists.